Area Forecast Discussion
Issued by NWS Portland, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KPQR 270932
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
231 AM PDT WED AUG 27 2014

.SYNOPSIS...A BROAD FLAT BUT RATHER STRONG UPPER LEVEL RIDGE WILL
REMAIN OVER THE PACIFIC NORTHWEST TODAY FOR ANOTHER VERY WARM DAY
INLAND...BUT A MARINE LAYER WILL KEEP THE COAST MUCH COOLER. A WEAK
SYSTEM WILL RIDE ACROSS THE UPPER RIDGE THROUGH WASHINGTON ON
THURSDAY...BEGINNING A TREND TOWARD COOLER TEMPERATURES INLAND... AND
INCREASED ONSHORE FLOW. A MORE SIGNIFICANT UPPER TROUGH WILL APPROACH
FRIDAY TO CONTINUE THE COOLING TREND AND THE ONSHORE FLOW. THIS UPPER
TROUGH WILL THEN SWING THROUGH THE REGION THIS WEEKEND FOR EVEN MORE
COOLING...MORE CLOUDS...AND POSSIBLY A FEW SHOWERS OVER THE HOLIDAY
WEEKEND.
&&

.SHORT TERM...TONIGHT THROUGH FRIDAY...THE RATHER STRONG UPPER RIDGE
THAT WAS EXPANDING INTO THE PACIFIC NORTHWEST TUESDAY WILL CONTINUE
OVER THE AREA TODAY. IT IS RATHER BROAD AND FLAT WITH SOME LIGHT
WESTERLY FLOW ALOFT OVER IT THROUGH WASHINGTON AND NORTHERN OREGON.
STILL...IT IS RATHER STRONG WITH 500 MB HEIGHTS OF 588 DM PUSHING
NORTH TOWARD EUGENE TODAY. THIS WILL KEEP THE AIR MASS QUITE WARM...
WHILE MAINTAINING OR EVEN REINFORCING A PERSISTENT BUT SHALLOW MARINE
LAYER NEAR THE COAST. THE MODELS EVEN SUGGEST SOME PATCHY DRIZZLE OR
MIST ALONG THE COAST THIS MORNING FROM THE FOG AND LOW CLOUD DECK.
LOW CLOUDS AND FOG AT THE COAST WILL HAVE TROUBLE CLEARING BACK
OFFSHORE MUCH IF AT ALL TODAY. INLAND PENETRATION OF THE LOW CLOUDS
THROUGH THE COASTAL GAPS WILL NOT MAKE A LOT OF PROGRESS
TODAY...PERHAPS GETTING TO KELSO ALONG THE COLUMBIA RIVER BUT NOT A
LOT FARTHER. AS A RESULT...EXPECT TEMPS TODAY TO BE NOT MUCH
DIFFERENT THAN THOSE ON TUESDAY.

THE MODELS SHOW THE UPPER RIDGE WEAKENING A BIT THURSDAY AS A SHORT
WAVE MOVES EASTWARD MAINLY THROUGH WASHINGTON...LOWERING 500 MB
HEIGHTS NEARLY 60 M. THIS SHOULD INCREASE THE ONSHORE FLOW SOME...
AND GIVE THE COASTAL LOW CLOUDS A CHANCE OF REACHING THE PORTLAND
AREA IN THE MORNING. THE INCREASED ONSHORE FLOW SHOULD LOWER TEMPS
INLAND AS WELL...CLOSER TO 80 NEAR PORTLAND TO THE MID TO UPPER 80S
IN THE SOUTH VALLEY. THE SHORT WAVE MAY ALSO BE ENOUGH TO GIVE A
BETTER CHANCE OF DRIZZLE TO THE COAST THURSDAY MORNING.

THE NEXT MORE SIGNIFICANT UPPER TROUGH WILL BE APPROACHING THE COAST
ON FRIDAY...CONTINUING THE TREND OF COOLING TEMPS...INCREASED ONSHORE
FLOW...AND MORE MORNING LOW CLOUDS INLAND. THE INITIAL PVA BAND IS
NOW FORECAST TO ARRIVE A BIT FASTER THAN MODEL RUNS OF 24 OR 48 HOURS
AGO SHOWED...COMING ONSHORE LATE FRIDAY AFTERNOON AND EVENING. THIS
MAY BE ENOUGH TO SPREAD A FEW SPRINKLES ONSHORE THROUGH FRIDAY NIGHT
AS A WEAK FRONTAL BOUNDARY PUSHES ONSHORE. TOLLESON

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
FRIDAY NIGHT THROUGH TUESDAY...A TROUGH APPROACHES THE WEST COAST ON
FRIDAY WHICH WILL BRING A CHANCE OF RAIN OVER THE WEEKEND. THE 12Z
ECMWF AND GFS BOTH BRING THE SYSTEM ONSHORE LATE FRIDAY NIGHT.
NORTHWESTERLY FLOW WILL BECOME DOMINANT OVER OUR AREA BEHIND THE
INITIAL COLD FRONT...WITH MULTIPLE IMPULSES BRINGING CHANCES OF RAIN
THROUGH SUNDAY EVENING.  12Z GFS SEEMS A LITTLE STRONG EARLY NEXT
WEEK BRINGING RAIN AND CLOUD COVER OVER OUR AREA AFTER TWO DAYS OF
NORTHWESTERLY FLOW...SO OPTED TO LEAN MORE TOWARDS ECMWF WITH SLIGHT
CHANCE OF RAIN MAINLY ALONG SOUTH WASHINGTON CASCADE AND COASTAL
RANGES. -MCCOY
&&

.AVIATION...VFR CONDITIONS PREVAILING ACROSS THE AREA. HOWEVER THE
COASTAL AREAS WILL HAVE IFR TO LIFR CONDITIONS THROUGH THE MORNING
HOURS WITH IMPROVEMENT IN THE AFTERNOON...THEN RETURN TO IFR
CONDITIONS THIS EVENING. SOME IFR CIGS WILL WORK ITS WAY UP THE LOWER
COLUMBIA RIVER TO THE KKLS AREA AND POSSIBLY A SCATTERED LAYER AROUND
1000 FT TO NEAR KPDX THIS MORNING. STRONGER ONSHORE FLOW TONIGHT INTO
THU SHOULD BRING A DEEPER MARINE LAYER WITH LOW MVFR CIGS REACHING
THE NORTH WILLAMETTE VALLEY AND SW WASHINGTON.

SOME LOCALIZED SMOKE FROM THE FIRES NEAR OAKRIDGE IN EASTERN LANE
COUNTY MAY REDUCE VSBY IN THAT AREA.

KPDX AND APPROACHES...VFR PREVAILING TODAY AND TONIGHT. THERE IS A 20
PERCENT CHANCE OF SCATTERED LAYER NEAR 1000 FT 14Z-16Z.
&&

.MARINE...PERSISTENT PATTERN CONTINUES WITH HIGH PRESSURE OVER THE NE
PACIFIC AND THERMAL LOW OVER NORTHERN CALIFORNIA. WINDS INCREASE SOME
THIS AFTERNOON BUT LIKELY REMAIN BELOW ADVISORY CRITERIA.  SEAS
REMAIN CHOPPY WITH SHORT PERIOD WIND WAVES DOMINATING.

HIGH PRESSURE SINKS SOUTHWARD THROUGH THE WEEK...MAKING WAY FOR OUR
NEXT LOW PRESSURE SYSTEM TO APPROACH FRIDAY NIGHT WITH BUILDING SWELL
LATE SATURDAY. WINDS TURN S TO SW OVER THE NEAR  SHORE WATERS ON THE
BACK SIDE OF THE LOW LATE SUNDAY WITH SOME DISAGREEMENT AMONG MODELS
AS TO TIMING OF SHIFT BACK TO N AND NW. BUT WINDS WILL REMAIN BELOW
20 KT DURING THE PERIOD OF UNCERTAINTY...SO IMPACT SHOULD BE MINIMAL.
TW/.H
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...NONE.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.